Conventional soda inclusive glasses are susceptible to environmental corrosion which occurs when sodium (Na) diffuses from or leaves the glass interior, as well as to retaining water on their surfaces in many different environments, including when used as automotive windows (e.g. backlites, side windows, and/or windshields). When water is retained or collects on automotive windows, the water may freeze (i.e. forming ice) in certain environments. The more water retained on a windshield, the higher power wiper motor(s) and/or wiper blade(s) required.
In view of the above, it is apparent that there exists a need in the art for (i) a coated article (e.g. coated glass or plastic substrate) that can repel water and/or dirt, and a method of making the same, (ii) a coated soda inclusive glass where the coating(s) reduces the likelihood of visible stains/corrosion forming; and/or (iii) a protective hydrophobic coating for window substrates that is somewhat resistant to scratching, damage, or the like.
It is known to provide diamond like carbon (DOC) coatings on glass. U.S. Pat. No. 5,637,353, for example, states that DOC may be applied on glass. Unfortunately, the DOC of the ""353 patent would not be an efficient hydrophobic coating and/or would not be an efficient corrosion minimizer on glass in many instances.
U.S. Pat. No. 5,900,342 to Visser et al. discloses a fluorinated DOC layer on an electrophotographic element. From about 25-65% fluorine content by atomic percentage is provided at an outermost surface, to provide for low surface energy in an attempt to make removal of xerographic toner easier. Unfortunately, this DOC inclusive layer of the ""342 patent would be too soft for use on a glass substrate in automotive applications and the like. Its apparent lack of sp3 Cxe2x80x94C bonds contribute to its softness. It is believed that continuous exposure to sun, rain, humidity, dust, windshield wipers, and/or the environment in general would cause the ""342 DOC layer to break down or degrade rather quickly and/or substantially over time.
Thus, there also exists a need in the art for a DOC inclusive layer that has sufficient hardness and durability to withstand the environment while still exhibiting satisfactory hydrophobic qualities.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a durable coated article that can shed or repel water (e.g. automotive windshield, automotive backlite, automotive side window, architectural window, etc.).
Another object of this invention is to improve the hydrophobic nature of a coated article by utilizing a surface (exterior and/or interior surface) having roughness such as defined by peaks and/or valleys. The formation or provision of nanostructures or other roughness on the surface results in an exterior surface of the coated article having both segments of solid material and segments of voids or air. Because liquids have high contact angles xcex8 in air (e.g., water""s contact angle xcex8 in air approaches 180 degrees), the provision of the voids at the surface of the coated article due to the nanostructures allows the coated article to exhibit increased and/or high contact angles xcex8, and thus be hydrophobic in nature. The nanostructures may be randomly or uniformly positioned in different embodiments.
Another object of this invention is to provide a coated article including a surface including roughness such that the average height or elevation xe2x80x9cdxe2x80x9d (i.e., xe2x80x9cdxe2x80x9d is measured from the bottom of a valley to the top of an adjacent peak) is from about 5 to 60 nm, more preferably from about 10-30 nm.
Another object of this invention is to provide a coated article with a surface including nanostructures dimensioned such that the average lateral spacing or gap xe2x80x9cgxe2x80x9d between adjacent nanostructures (i.e., xe2x80x9cgxe2x80x9d is measured from the peak of one nanostructure to the peak of an adjacent nanostructure) is from about 10-100 nm, more preferably from about 10-50 nm.
The aforesaid surface(s) may be: (i) an exterior surface of the coated article, (ii) a surface of an underlying substrate, such as a glass substrate, on which a coating(s) is to be provided, and/or (iii) a surface of an intermediate layer provided between the underlying substrate and an exterior diamond-like carbon (DOC) inclusive layer.
Another object of this invention is to provide a coated article, wherein a layer of the coating includes sp3 carbon-carbon bonds and has a wettability W with regard to water of less than or equal to about 23 mN/m, more preferably less than or equal to about 21 mN/m, and most preferably less than or equal to about 20 mN/m, and in most preferred embodiments less than or equal to about 19 mN/meter. This can also be explained or measured in Joules per unit area (mJ/m2).
Another object of this invention is to provide a coated article, wherein a layer of the coating includes sp3 carbon-carbon bonds and has a surface energy xcex3c of less than or equal to about 20.2 mN/m, more preferably less than or equal to about 19.5 mN/m, and most preferably less than or equal to about 18 mN/m.
Another object of this invention is to provide a coated article, wherein a DOC inclusive layer of the coating has an initial (i.e. prior to being exposed to environmental tests, rubbing tests, acid tests, UV tests, or the like) water contact angle xcex8 of at least about 100 degrees, more preferably of at least about 120 degrees, even more preferably of at least about 130 degrees, and most preferably of at least about 145 degrees. The article""s initial contact angle xcex8 may be as high as 175 degrees in certain embodiments. In certain embodiments the article""s contact angle may increase over time upon exposure to environmental elements (as graphitic sp2 Cxe2x80x94C bonds wear off) while in other embodiments the article""s contact angle may decrease over time upon such exposure.
Another object of this invention is to provide a DOC inclusive layer for coating on a substrate, wherein at least about 15% (more preferably at least about 25%, and most preferably at least about 30%) of the bonds in a DOC inclusive layer are sp3 carbon-carbon (Cxe2x80x94C) bonds; and wherein the DOC inclusive layer includes by atomic percentage at least about 5% hydrogen (H) atoms (more preferably at least about 10% and most preferably at least about 15%) taking into consideration either the DOC inclusive layer""s entire thickness or only a thin layer portion thereof (i.e., the layer is hydrogenated). In certain embodiments, an increased percentage of H atoms may be provided near the DOC inclusive layer""s outermost or exterior surface (e.g., outermost 10 angstroms of the layer) to be contacted by water or the like.
Another object of this invention is to provide a coating for a glass substrate, wherein a DOC inclusive layer of the coating includes a greater number of sp3 carbon-carbon (Cxe2x80x94C) bonds than sp2 carbon-carbon (Cxe2x80x94C) bonds.
Another object of this invention is to provide a coated glass article that is abrasion resistant.
Yet another object of this invention is to fulfill any or all of the above listed objects and/or needs.
Generally speaking, this invention fulfills any or all of the above described needs or objects by providing a coated article comprising:
a substrate;
a hydrophobic layer including diamond-like carbon (DOC) and sp3 carbon-carbon bonds provided on said substrate; and
wherein an exterior surface of said hydrophobic layer has a roughness sufficient such that the hydrophobic layer has an initial contact angle xcex8 with a sessile drop of water thereon of at least about 100 degrees.
This invention further fulfills any or all of the above described needs and/or objects by providing a method of making a coated article comprising the steps of:
providing a substrate; and
depositing a hydrophobic layer including sp3 carbon-carbon bonds on the substrate over top of a surface having a roughness so that the resulting layer including sp3 carbon-carbon bonds has a roughness at an exterior surface thereof sufficient such that the hydrophobic layer has an initial contact angle xcex8 with a sessile drop of water thereon of at least about 100 degrees.
This invention will now be described with respect to certain embodiments thereof, along with reference to the accompanying illustrations.